Inertia trip for circuit breakers



y 1950 L. w. DYER 2,508,148

INERTIA TRI P- FOR CIRCUIT BREAKERS Filed Jan. 13, 1945 I I I I l a l WITNESSES: F 43 INVENTOR 54% I L/oyah/Dyn Q BY ATTORNEY Patented May 16, 1950 INERTIA TRIP FOR cmcurr BREAKERS Lloyd W. Dyer, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 13, 1945, Serial No. 572,597

7 Claims.

This invention relates generally to electric circuit breakers, and more particularly to high speed circuit breaker operating and trip mechanisms.

It sometimes happens that in closing a circuit breaker against a short circuit, the magnetic forces encountered as soon as the arcing tips touch are high enough to prevent complete closing of the main breaker contacts, and consequently the breaker may be damaged due to excessive arcing. Of course, relays may be employed which will trip the breaker when the breaker is closed on a fault, but these are too slow in operation to afiord adequate protection against excessive arcing in the event the breaker stalls during a circuit closing operation.

In the copending application of Alfred Loos, Serial No. 470,939, Circuit breakers, filed December 31, 1942, now abandoned, and assigned to the same assignee as this invention, there is disclosed a means for tripping the breaker in the event the breaker stalls during circuit closing operation for any reason, but the tripping means of Loos is operated by reverse movement of the breaker.

It is, therefore, one object of this invention to provide novel means for instantaneously tripping the breaker free of its operating mechanism in the event the breaker suddenly stops or stalls during a circuit closing operation.

A more specific object of this invention is to provide inertia means which is responsive to the sudden stoppingor stalling of a circuit breaker during its circuit closing movement, to instantaneously trip said breaker free of its operating mechanism.

These and other objects of this invention willbecome more apparent upon consideration of the following detailed description of a preferred embodiment thereof, when taken in connection with the attached drawing, in which:

Figure 1 is a diagrammatic view of a circuit breaker and circuit breaker operating mechanism embodying this invention, with a control circuit for the mechanism illustrated diagrammatically;

Fig. 2 is an enlarged side elevation view of a part of the mechanism illustrated in Fig. 1, but

at a difierent position; and

Fig. 3 is a side elevation view of the mechanism parts illustrated in Fig. 2, but at a different position.

The circuit breaker illustrated on the drawing is provided with stationary contacts 2 adapted to be bridged by a movable bridging contact structure 4. Stationary contacts 2 include main contact portions 6 adapted to be engaged by a main bridging contact bar 8; Stationary contacts 2 also include angularly extending arcing contact portions l0 adapted to be engaged by a resilient bridging member I2, preferably comprising a laminated member made up of a plurality of leaf springs.

In the closed circuit position shown in full lines in Fig. l, bridging member l2 for the arcing contact portions I0 is in substantially straightened condition. However, bridging member l2 normally assumes the curved position shown in dotted lines in Fig. 1, so that when bridging structure 4 is moved away from stationary contacts 2, main bridging contact 8 will disengage main contact portion 6 while bridging member l2 remains engaged with arcing contact portions l0, so that the arc will be drawn between bridging member 12 and arcing contact portions 10. In closing the breaker, bridging member 12 will engage arcing contact portions l0 before main bridging contact 8 engages main contact portion 6.

Bridging contact structure 4 is mounted on the lower end of a lift rod I4, and the lift rod is biased downwardly in a direction to open the circuit by a coil spring [6, which reacts between a shoulder 20 provided on the lift rod, and a stationary frame member I8. Unless bridging contact structure 4 is held by other means at the closed circuit position, it is apparent that spring l6 will maintain bridging contact structure 4 at an open circuit position. 1

Lift rod I4 is adapted to be actuated by an operating lever 22 pivotally connected therewith as at 24. Operating lever 22 is pivotally mounted intermediate its ends as at 26 on a stationary frame member 21, and is pivotally connected at its other end with an operating rod 30, as by a pivot pin 28.

Operating rod 30 is adapted to be connected with a motive means for closing the breaker contacts by a trip-free mechanism, such for example, as the trip-free mechanism disclosed in the copending application of J. M. Cumming et al. on Circuit breakers, Serial No. 437,669, filed April 4, 1942, now Patent No. 2,403,082, issued July 2, 1946, and assigned to the same assignee as this invention. Such a trip-free mechanism comprises, in general, a trip-free lever 32 which is pivotally connected with operating rod at intermediate the ends of the lever as by a pivot pin 3 l. Trip-free lever 32 is pivotally connected at one end, as by a pivot pin 34, with an actuating lever 36 adjacent one end of the latter, and the actuating lever is adapted to be. pivotally supported at its opposite end by a pivot pin 38. Actuating lever 36 is biased for movement about its'supporting pivot 38 in a clockwise direction as viewed in Fig. 1, by a coil compression spring 39. Actuating lever 36 is, however, normally prevented from rotating under the influence of biasing spring 39, by engagement of pivot pin 34 thereof by a latch lever 48 pivotally mounted on a stationary frame member by means of a pivot pin 42. Trip-free lever 32 carriesa latch pin 43, which, in the normal position of the parts as shown in Fig. 1, is substantially in alignment with pivot pin 38, and is adapted at this position to be held by a latch lever 44 pivotally mounted on astationary frame member as by a pivot pin 46. The trip-free lever 32 is provided at its other end with a latch release projection 4'! adjacent to, but spaced from, pivot 34, for a purpose to be hereinafter'described. Actua-ting lever 36 is adaptedto-be connected with a motive means 50 by means of a connecting rod 48 pivotally connected to the actuating lever as at 52. Motive means :58 may be of any desired type, such'for exampleaas a'solenoid having'a core attached to connecting rod-4'3, orit may be afluid motor having a piston attached'to connecting rod 48.

With the parts in the positions shown in Fig. 1, it is apparent that bridging contact structure 4 of the-circuitbreaker is held latched in its closed circuit position'by latches Y40 and). In order to permit the breaker to be opened by spring 16, there-is provided'ian integral extension 5401? latch lever 44 which isadapted collie-engaged by a-solenoid plunger lit, when its 'trip'coil 53 is energized.

n at

lrip coil 58 is shown as connected in control circuit which may be energized by any suitable 'means,,such for example as a battery til, and the ciently to attract plunger 54 and close the control circuit "by bridging .its contacts 62. lihis energizes trip coil 58,-,causing its plunger '36 to move upwardly and engagelatchextensional, to v release la'tchilever4'4 'froni-pin43 on trip -iree lever 32. This notonlyreleases bridging contact structure 1 cl the breaker for'rapidmovcment to'open 'circuit'position by spring ifiybut also disconnects the :movingcontact-structure from motive means tidsince trip-free lever 32 is free to move independently of actuating lever 36 to the position shown in Fig. 3. During the last part of opening movement of trip-free lever 32, latch release projection 41 thereon is adapted to engage-and move latch lever 4i] to release pivot pin 34, and thus permit spring '39 to move-actuating lever 36 in a clockwise direction about its pivot 38 as viewed in Fig. 1. Such clockwise rotation of actuating lever 36 raises connecting-rod 48 and pivot pin as connecting the actuating lever to trip-free lever 32, and accordingly rotates trip-free lever 32 in a clockwise direction with respect to its pivot 3| on operating rod 30. lhis resetting movement of trip-free lever 32 and actuating lever '36 caused by spring 39, continues until the parts attain the position shown in Fig. 2 of the drawing, where latch pin 43 of the trip-free lever will be reengaged by latch lever 44.

With the parts in the position shown in Fig. 2,

iii

it will be observed that motive means 50 is now operatively connected with operating rod 30, so that the motive means may be energized to pull connecting rod 48 downwardly and reclose the circuit breaker. Reclosing movement of the breaker continues until pivot pin 34 connecting trip-free lever 32 and actuating lever 36 is reengaged by latchlever 40, which is the position of the parts illustrated in full-lines in Fig. 1.

As previously pointed out, it sometimes happens that when the circuit breaker is closed against a short circuit or similar heavy overload, the magnetic forces encountered when bridging contact [2 first touches arcing contact portions [0, resist closing-of the contacts, and if of suffi- --cient magnitude may stall the breaker as soon as bridging contact I2 engages arcing contact portions It). In order to prevent undue damage to the breaker in the event of the occurrence of such a condition, means is provided to open the breaker as fast as,-possible, comprising an inertia weight =12 which is :pivotally mounted as at H on a lever 13 :pivotally connected with operating rod '30 as at :14. Lever '13 is pivotally mounted intermediate its-ends on a stationary member I5. Pivotal movement ofinertia weight 12 with respect to lever 13 is limited by the'spaced stop 76 provided on the lever. Inertia weight 12 is provided with an operating projection l8'which extends "into proximity with the long leg of a generally Ushaped actuator lever pivotally mounted on a stationary frame member-as at 82. The short leg 84 :of the 1U-shapedactuating lever is adapted'to be connected with latch lever 44, by means of a pivotedconnecting link 86.

It will be observed that in the 'closed position of the circuit breaker illustrated in full lines in Fig. 1, operating projection 18 of inertia weight .2 cannot engage leg -80 of the actuator lever upon pivotal movement of the inertia weight on pivot 14. When {latch-44 is released by trip coil 58 or other means to efiecta circuit opening operation of the breaker, leg 80 of the actuator lover will be moved waway'from the path of move- ,ment of operating projection 18 or" the inertia weight. However, when the breaker-isclosed, the long leg 30 of theaCtuator lever will occupy the position shown inFig. l'closely adj acent-thepath of movement of operating projection 18 of the inertia weight, so :that if the breaker is stopped suddenly, or'the rate of movement thereof suddenly decreases, :for example, when the arcing contacts touch or even before in theleventof failure of the closing means, inertia weight -12 will tend to continue :its movement at the same rate and as a result will :rotate in-a clockwise direction about its pivot --l I so that operating projection -18 thereof will engage the long-leg 8G orthe actuator lever and 'cause'it to release latch lever vIt will now clears long leg 80 of theactuator lever when the circuit breaker isat its :fully closed position (Fig.

1), because :the parts come to a sudden :halt at this position and it is not desired that the inertia weight 12 bereifective itocpen-the breakerat the -ful1y closed .position. However, it is apparent that the inertia weight 12 is effective whenever rotation thereof occurs relative 'to operating rod 30 during the circuit closing movement at any position'of the breaker contacts except the fully closed position, to engage the long leg 8|] of the actuator lever to cause release of latch 44, and zheireby permit rapid opening of the breaker conac s.

From the foregoing, it is apparent that this invention provides a means for effecting as rapid an opening of the breaker contacts as possible whenever the contacts stall or hesitate in movement during a circuit closing operation. This may be due to excessive magnetic forces encountered or to failure of the operating mechanism, as previously pointed out, but in any event, it is essential that rapid opening of the breaker occur as soon as possible in order to prevent undue damage to the breaker.

Having disclosed a preferred embodiment of the invention in accordance with the patent statutes, it is desired that this invention be not limited to this particular structure, inasmuch as it will be apparent, particularly to persons skilled in the art, that many modifications and changes may be made in this particular construction without departing from the broad spirit and scope of this invention. It is, therefore, desired that this invention be interpreted as broadly as possible, and that it be limited only as required by the prior art.

I claim as my invention:

1. In a circuit breaker, a circuit interrupter, means operable to initiate actuation of said interrupter to an open circuit position, operating means operable to initiate closing of said interrupter, and inertia means mounted on a part of the interrupter which moves at least during a circuit closing operation thereof so as to be operative solely in response to the occurrence of a predetermined decrease in the rate of movement of said interrupter in the circuit closing direction during a circuit closing operation before full closed circuit position is reached, to automatically cause said opening means to open said interrupter.

2. In a circuit breaker, a circuit interrupter, means for initiating actuation of said interrupter to an open circuit position, operating means operable to initiate closing of said interrupter, an inertia weight mounted for limited relative movement on a part movable with said interrupter at least during circuit closing movement, and means operated by relative movement of said weight caused by a predetermined decrease in the rate of movement of said interrupter during a circuit closing operation before full closed circuit position is reached, to automatically cause said actuating means to open said interrupter.

3. In a circuit breaker, circuit interrupting means biased to an open circuit position, operating means operable to close said interrupter, means releasably coupling said operating means to said interrupter, inertia means mounted on a part of the interrupter which moves at least during a circuit closing operation thereof so as to be operative solely in response to the occurrence of a predetermined decrease in the rate of movement of said interrupter in the circuit closing direction during a circuit closing operation before full closed circuit position is reached, to automatically effect release of said coupling to permit rapid opening of said interrupter.

4. In a circuit interrupter, relatively stationary and movable contact means, operating means for initiating movement of said movable contact means into engagement with said stationary contact means to close the circuit, means for initiating movement of said movable contact means away from said stationary contact means to open the circuit, and inertia means mounted on a part movable with said movable contact means at least during a circuit closing operation so as to be operative solely in response to the occurrence of a predetermined decrease in the rate of movement of said interrupter in the circuit closing direction during a circuit closing operation before full closed circuit position is reached to automatically cause said circuit opening means to open said interrupter.

5. In a circuit interrupter, relatively stationary and movable contact means, operating means for initiating movement of said movable contact means into engagement with said stationary contact means to close the circuit, means for initiating movement of said movable contact means away from said stationary contact means to open the circuit, an inertia weight mounted for limited relative movement on a part movable with said movable contact means at least during circuit closing movement, and means positioned adjacent the path of movement of a member movable with said weight, except for a small portion of said path of movement at and closely adjacent closed circuit position, so as to be engaged by said member upon relative movement of said weight caused by a predetermined decrease in the rate of movement of said interrupter during a circuit closing operation before full closed circuit position is reached to automatically cause said circuit opening means to open said interrupter.

6. In a circuit breaker, a circuit interrupter, operating means operable to open and close said interrupter, and inertia means mounted on a part of the interrupter which moves at least during a circuit closing operation thereof so as to be operative solely in response to the occurrence of a predetermined decrease in the rate of movement of said interrupter in the circuit closing direction during a circuit closing operation before full closed circuit position is reached, to automatically cause said operating means to open said interrupter.

7. In a circuit breaker, a circuit interrupter, operating means operable to open and close said interrupter, an inertia weight mounted for limited relative movement on a part movable with said interrupter at least during a circuit closing operation, and means operated by relative movement of said weight caused by a predetermined decrease in the rate of movement of said interrupter during a circuit closing operation before full closed circuit position is reached, to automatically cause said operating means to open said interrupter.

LLOYD W. DYER.

REFERENCES CITED The following references are of record in the 5 file of this patent:

UNITED STATES PATENTS- 

